warning {base} | R Documentation

## Warning Messages

### Description

Generates a warning message that corresponds to its argument(s) and (optionally) the expression or function from which it was called.

### Usage

    warning(..., call. = TRUE)
    suppressWarnings(expr)

### Arguments

`...` | character vectors (which are pasted together with no separator), a condition object, or `NULL`.
`call.` | logical, indicating if the call should become part of the warning message.
`expr` | expression to evaluate.

### Details

The result depends on the value of `options("warn")` and on handlers established in the executing code.

`warning` signals a warning condition by (effectively) calling `signalCondition`. If there are no handlers or if all handlers return, then the value of `warn` is used to determine the appropriate action. If `warn` is negative warnings are ignored; if it is zero they are stored and printed after the top–level function has completed; if it is one they are printed as they occur and if it is 2 (or larger) warnings are turned into errors.

If `warn` is zero (the default), a top-level variable `last.warning` is created. It contains the warnings which can be printed via a call to `warnings`.

Warnings will be truncated to `getOption("warning.length")` characters, default 1000.

While the warning is being processed, a `muffleWarning` restart is available. If this restart is invoked with `invokeRestart`, then `warning` returns immediately.

`suppressWarnings` evaluates its expression in a context that ignores all warnings.

### References

Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.

### See Also

`stop` for fatal errors, `warnings`, and `options` with argument `warn=`.

### Examples

    testit <- function() warning("testit")
    testit() ## shows call
    testit <- function() warning("problem in testit", call. = FALSE)
    testit() ## no call
    suppressWarnings(warning("testit"))

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